(function(win, doc){
    var docEl = doc.documentElement,
        resizeEvt = 'oritationchange' in window ? 'oritationchange' : 'resize',
        recalc = function(){
            var clientWidth = docEl.clientWidth;
            var clientHeight = docEl.clientHeight;
            if (!clientWidth) return;
            if (clientWidth > 720) {
            	clientWidth = 720;
            }
            docEl.style.fontSize = 100 * (clientWidth / 1080) + 'px';
        }
    if (!doc.addEventListener) return;
    win.addEventListener(resizeEvt, recalc, false);
    doc.addEventListener('DomContentLoaded', recalc, false);
    recalc();
})(window, document)